The present invention generally relates to load-lifting apparatuses and, more particularly, to vertically-adjustable car seats.
Car seats with vertical-adjustment capability are known in the automobile industry. The seat portion is connected to a carrier member which is in turn pivotally connected to a base member by support legs. An actuating handle is operative for moving the carrier member between lowered and raised positions relative to the base member.
It has been proposed to use one pair of support legs at the front of the seat and another pair of support legs at the rear. Alternatively, guide tracks have been used at the rear of the seat. It has further been proposed to use gears or gear segments intermediate the base and carrier members for improving force transmission. A rotary gear has been turnably mounted on the frame of the seat, and a cooperating gear has been mounted on the support legs for meshing engagement with the rotary gear. Alternatively, the rotary gear has been mounted on the support legs and a stationary meshing gear has been mounted on the seat frame.
All of the known prior-art proposals for adjusting the position of car seats are characterized in that the angular distance through which the support legs are moved corresponds to the angular distance through which the rotary gear is moved. The known proposals thus have the disadvantage that the torque necessary for turning the actuating handle is relatively high when the carrier member is closest to the base member, that is when the carrier member is in its lowered position, and further that the torque is relatively low when the carrier member is furthest from the base member, that is when the carrier member is in its raised position. Therefore, when the actuating handle is turned, the magnitude of the turning torque is continuously varying, and the torque required at any particular time will depend upon the relative position between the carrier and base members. This changing torque characteristic is highly disadvantageous for a user.